Solid-state imaging apparatus having a solid-state imaging device and a signal processing circuit and method for driving the solid-state imaging device

ABSTRACT

A solid-state imaging apparatus includes a solid-state imaging device and a signal processing circuit. The solid-state imaging device includes: a plurality of photoelectric converting sections provided with color filters having different spectroscopic characteristics, and each converting light incident thereon into a charge and accumulating the charge, and a plurality of vertical charge transfer sections for vertically transferring the charge read from each of the photoelectric converting sections. A plurality of reading operations to read the charges accumulated in the photoelectric converting sections to the plurality of the vertical charge transfer sections are performed within a time duration for scanning an image for one image plane, and the charges read from the photoelectric converting sections are transferred through the vertical charge transfer section separately for each of the reading operations. The signal processing circuit includes: a plurality of color separation circuits each for performing color separation of signals based on the charges read by the plurality of reading operations and transferred separately; and a synthesis circuit for synthesizing the signals sent by the color separation circuits and outputting the resultant signal.

This application is a division of U.S. patent application Ser. No.08/779,333, filed Jan. 6, 1997 now U.S. Pat. No. 5,966,174 which is aFile-Wrapper Continuation Application of Ser. No. 08/449,742, filed May25, 1995 (abandoned).

The entire disclosure of U.S. patent application Ser. No. 08/779,333,filed Jan. 6, 1997 is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging apparatus havinga solid-state imaging device and a signal processing circuit, used in avideo camera and the like and a method for driving the solid-stateimaging device.

2. Description of the Related Art

Recently, solid-state imaging devices and signal processing circuitsused for such solid-state imaging devices has been improved inperformance and are in use in a video camera for consumer use.

A conventional solid-state imaging device and a signal processingcircuit used for such a solid-state imaging device described in JapaneseLaid-Open Patent Publication No. 2-87685 will be described withreference to FIG. 18.

Such a conventional solid-state imaging device includes photoelectricconverting sections arranged two dimensionally and a vertical chargetransfer section for vertically transferring charges which are output bythe photoelectric converting sections. A plurality of reading operationsare performed within a period in which images corresponding to one imageplane are formed, and the charges which are output are mixed in thevertical charge transfer section. The vertical charge transfer sectionoutputs the result.

For example, the two reading operations are performed within theabove-described period. A charge Q1 read in the first reading operationis accumulated in time duration t1, and a charge Q2 read in the secondreading operation is accumulated in time duration t2, which is differentfrom time duration t1. FIG. 18 illustrates the photoelectric convertingcharacteristic of the conventional solid-state imaging device. In FIG.18, the vertical axis represents the intensity of light, and thehorizontal axis represents the level of the voltage obtained byconverting the quantity of the output charge. The solid line indicatessuch a characteristic of the charge Q1, and the dashed line indicatessuch a characteristic of the charge Q2. The chain line represents such acharacteristic of a charge Q3 obtained as a result of the mixture of thecharges Q1 and Q2. As is illustrated in FIG. 18, the voltage based onthe charge Q1 which is output in the first reading operation reaches asaturation level of the photoelectric converting section when theintensity of light becomes B. The voltage based on the charge Q2 whichis output in the second reading operation reaches a saturation level ofthe photoelectric converting section when the intensity of light becomesD. The charge Q2 provides a wide dynamic range, but provides a low S/Nratio when the intensity of light is low due to the low signal levelthereof. The charge Q1 provides a narrow dynamic range, but provides ahigh S/N ratio due to the high signal level thereof. Thus, the charge Q3provides a wide dynamic range and a high S/N ratio even if the intensityof light is low.

A solid-state imaging apparatus having the above-described structure hasdrawbacks. Specifically, the saturation levels of the photoelectricconverting sections corresponding to different pixels are not uniform.Thus, the knee point of the charge Q3 at which the curve representingthe photoelectric converting characteristic turns drastically isdifferent among different pixels. Such non-uniformity is represented asnoise having a fixed pattern in an area of a video image having a highluminance, which significantly deteriorates the quality of the image.

Moreover, in the case where a plurality of color filters havingdifferent spectroscopic characteristics are provided in order to displaya color image by a single solid-state imaging apparatus, colorseparation cannot be done due to the photoelectric convertingcharacteristic having a knee point.

SUMMARY OF THE INVENTION

A method for driving a solid-state imaging device is provided. Thesolid-state imaging device includes a plurality of photoelectricconverting sections arranged two dimensionally and respectivelycorresponding to a plurality of pixels, and a vertical charge transfersection for vertically transferring a charge read from each of thephotoelectric converting sections. The method of the invention includesthe steps of: performing a plurality of reading operations within a timeduration for scanning an image for one image plane, thereby readingcharges accumulated in the photoelectric converting sections to thevertical charge transfer section; and transferring the charges read fromthe photoelectric converting sections through the vertical chargetransfer section separately for each of the reading operations.

According to another aspect of the invention, a solid-state imagingapparatus is provided. The solid-state imaging apparatus includes asolid-state imaging device and a signal processing circuit. Thesolid-state imaging device includes: a plurality of photoelectricconverting sections provided with color filters having differentspectroscopic characteristics, and each converting light incidentthereon into a charge and accumulating the charge, and a plurality ofvertical charge transfer sections for vertically transferring the chargeread from each of the photoelectric converting sections. A plurality ofreading operations to read the charges accumulated in the photoelectricconverting sections to the plurality of the vertical charge transfersections are performed within a time duration for scanning an image forone image plane, and the charges read from the photoelectric convertingsections are transferred through the vertical charge transfer sectionseparately for each of the reading operations. The signal processingcircuit including: a plurality of color separation circuits each forperforming color separation of signals based on the charges read by theplurality of reading operations and transferred separately; and asynthesis circuit for synthesizing the signals sent by the colorseparation circuits and outputting the resultant signal.

In one embodiment of the invention, the charges from fewer than all thephotoelectric converting sections are read in at least one of theplurality of reading operations.

In another embodiment of the invention, the charges from all thephotoelectric converting sections are read in each of the plurality ofthe reading operations.

In still another embodiment of the invention, the charges from at leasttwo adjacent photoelectric converting sections in each of the pluralityof reading operations are mixed together in the vertical charge transfersection.

In still another embodiment of the invention, the charges from at leasttwo adjacent photoelectric converting sections in at least one of theplurality of reading operations are mixed together in the verticalcharge transfer section, and the charges read in the remaining readingoperations are vertically transferred with no mixture.

In still another embodiment of the invention, the photoelectricconverting sections are provided with color filters having differentspectroscopic characteristics from one another.

In still another embodiment of the invention, the image for one imageplane is scanned within one field in a television scanning system.

In still another embodiment of the invention, the solid-state imagingdevice is irradiated by light for different time durations for theplurality of reading operations.

In still another embodiment of the invention, the plurality of readingoperations are performed within a vertical blanking period in atelevision scanning system.

According to still another aspect of the invention, a solid-stateimaging apparatus is provided. The solid-state imaging apparatusincludes a solid-state imaging device and a signal processing circuit.The solid-state imaging device includes: a plurality of photoelectricconverting sections provided with color filters having differentspectroscopic characteristics, and each converting light incidentthereon into a charge and accumulating the charge, and a plurality ofvertical charge transfer sections for vertically transferring the chargeread from each of the photoelectric converting sections. A plurality ofreading operations to read the charges accumulated in the photoelectricconverting sections to the plurality of the vertical charge transfersections are performed within a time duration for scanning an image forone image plane, and the charges read from the photoelectric convertingsections are transferred through the vertical charge transfer sectionseparately for each of the reading operations. The signal processingcircuit includes: a synthesis circuit for synthesizing signals based onthe charges read by the plurality of reading operations and transferredseparately, and a color separation circuit for performing colorseparation of the signals sent by the synthesis circuit and outputtingthe resultant signals.

In one embodiment of the invention, the synthesis circuit includes: aclip circuit for receiving a first part of the signals based on thecharges read by the plurality of reading operations and transferredseparately and clipping the signals each having a level exceeding aprescribed level to reduce the levels of such signals to the prescribedlevel; an addition circuit for adding the signals sent by the clipcircuit and a second part of the signals; and a tone compensationcircuit for compensating for tone characteristics of the signals sent bythe addition circuit.

In another embodiment of the invention, the synthesis circuit includes:an amplification circuit for receiving a first part of the signals basedon the charges read by the plurality of reading operations andtransferred separately and amplifying the first part of the signals at aconstant amplification factor; a comparison circuit for comparing asecond part of the signals with a reference signal level; and aselection circuit for selecting one of the first part and the secondpart, based on the output from the comparison circuit.

In still another embodiment of the invention, the synthesis circuitincludes: a subtraction circuit for subtracting a second part of thesignals based on the charges read by the plurality of reading operationsand transferred separately from a first part of the signals; anamplification circuit for amplifying the second part of the signals at aconstant amplification factor; a comparison circuit for comparing thefirst part of the signals with a reference signal level; and a selectioncircuit for selecting one of the signals sent by the amplificationcircuit and the signals sent by the subtraction circuit, based on theoutput from the comparison circuit.

Thus, the invention described herein makes possible the advantages of(1) providing a solid-state imaging apparatus and a method for drivingthe solid-state imaging device for substantially eliminatingdeterioration of the image quality caused by non-uniform saturationlevels in the photoelectric converting sections; and (2) providing asolid-state imaging apparatus and a method for driving the solid-stateimaging device for displaying a color image using a plurality of colorfilters having different spectroscopic characteristics.

These and other advantages of the present invention will become apparentto those skilled in the art upon reading and understanding the followingdetailed description with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a solid-state imaging device in asolid-state imaging apparatus in a first example according to thepresent invention.

FIG. 2 is a graph illustrating the timing at which pulses are input, andthe relationship between such timing and the quantity of charges fromphotoelectric converting sections in the solid-state imaging deviceshown in FIG. 1.

FIG. 3 is a block diagram of a signal processing circuit in the firstexample.

FIG. 4 is a graph illustrating the photoelectric convertingcharacteristics of signals obtained by first and second readingoperations performed by the solid-state imaging device shown in FIG. 1.

FIG. 5 is a graph illustrating the timing at which pulses are input, andthe relationship between such timing and the quantity of charges fromphotoelectric converting sections in a second example according to thepresent invention.

FIG. 6 is a schematic plan view of a solid-state imaging device in asolid-state imaging apparatus in a third example according to thepresent invention.

FIG. 7 is a waveform diagram illustrating first and second readingoperations performed by the solid-state imaging device shown in FIG. 6.

FIG. 8 is a schematic plan view of a solid-state imaging device in asolid-state imaging apparatus in a fourth example according to thepresent invention.

FIG. 9 is a block diagram of a signal processing circuit in the fourthexample.

FIG. 10 is a graph illustrating the photoelectric convertingcharacteristics of RGB signals in the fourth example.

FIG. 11 is a block diagram of a signal processing circuit in a fifthexample.

FIG. 12 is a graph illustrating the photoelectric convertingcharacteristics of signals before and after being sent to a dekneecircuit.

FIG. 13 is a block diagram of a signal processing circuit in the sixthexample.

FIG. 14 is a block diagram of a signal processing circuit in a seventhexample.

FIG. 15 is a graph illustrating the photoelectric convertingcharacteristics of signals obtained in the seventh example.

FIG. 16 is a schematic plan view of a solid-state imaging device of asolid-state imaging apparatus in an eighth example according to thepresent invention.

FIG. 17 is a block diagram of a signal processing circuit in the eighthexample.

FIG. 18 is a graph illustrating the photoelectric convertingcharacteristics of signals obtained in a conventional solid-stateimaging device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described by way ofillustrative examples with reference to the accompanying drawings.

EXAMPLE 1

With reference to FIGS. 1 through 4, a solid-state imaging apparatus ina first example according to the present invention will be described. Inthis specification, a solid-state imaging apparatus includes asolid-state imaging device and a signal processing circuit used for thesolid-state imaging device.

FIG. 1 is a schematic plan view illustrating the structure of asolid-state imaging device 100 in the first example. The solid-stateimaging device 100 includes a plurality of photoelectric convertingsections 1 arranged in a matrix, namely in rows and columns. Eachphotoelectric converting section 1 acts as a light receiving element andcorresponds to one pixel. The solid-state imaging device 100 furtherincludes a plurality of vertical charge transfer sections 2, drivingpulse input terminals 3 a through 3 f, horizontal charge transfersections 4 a and 4 b, output amplifiers 5 a and 5 b, and outputterminals 6 a and 6 b. Each of the plurality of vertical charge transfersections 2 includes a plurality of transfer gates and a plurality ofsemiconductor regions below (not shown) the respective transfer gates.The transfer gates in each vertical charge transfer section 2 arearranged in a line. The plurality of vertical charge transfer sections 2and the plurality of columns of photoelectric converting sections 1 areprovided to be adjacent to each other. Two adjacent photoelectricconverting sections 1 a and 1 b in the same column form a pair. Thephotoelectric converting section 1 a is adjacent to three transfer gates2 a, 2 b and 2 c; and the photoelectric converting section 1 b isadjacent to three transfer gates 2 d, 2 e and 2 f. The transfer gates 2a through 2 f are connected to the driving pulse input terminals 3 athrough 3 f, respectively. Although not shown in FIG. 1 completely, allthe transfer gates are respectively connected to the driving pulse inputterminals. For example, the transfer gate 2 a is connected to thedriving pulse input terminal 3 a; and the transfer gate 2 b is connectedto the driving pulse input terminal 3 b. The horizontal charge transfersections 4 a and 4 b are located to be substantially perpendicular tothe vertical charge transfer sections 2 and adjacent to one end of eachvertical transfer section 2. The horizontal charge transfer section 4 ais connected to the output amplifier 5 a, which is connected to theoutput terminal 6 a. The horizontal charge transfer section 4 b isconnected to the output amplifier 5 b, which is connected to the outputterminal 6 b.

FIG. 2 is a timing chart illustrating the operation of the solid-stateimaging device 100. øV1 through øV6 are respectively pulses which areinput to the driving pulse input terminals 3 a through 3 f. In FIG. 2,each of the rectangular boxes having two diagonal lines thereinindicates that a pulse is input to the corresponding driving pulse inputterminal repeatedly as is shown in the enlarged section within theperiod shown by the box. For example, the left box corresponding to øV1indicates that a pulse having a “high” voltage is input repeatedlyduring time duration t1.

The solid-state imaging device 100 operates in the following manner.

In a first field, when light is incident on the solid-state imagingdevice 100, the light is converted into an electric charge by thephotoelectric converting sections 1, and the charge is accumulatedtherein. In a vertical blanking period of a TV scanning system, a “high”voltage is applied to the driving pulse input terminal 3 e. By suchvoltage application, a charge Q1 accumulated in the photoelectricconverting section 1 b is read to the semiconductor region below thetransfer gate 2 e. In this manner, a first reading operation isperformed. Immediately after the first reading operation is finished,the charge Q1 in the photoelectric converting section 1 b is totallydischarged to the substrate of the solid-state imaging device 100,thereby leaving no charge in the photoelectric converting section 1 b.

Within the same vertical blanking period, a “high” voltage is applied tothe driving pulse input terminal 3 b. By such voltage application, acharge Q2 accumulated in the photoelectric converting section 1 a isread to the semiconductor region below the transfer gate 2 b,independently from the charge Q1. In this manner, a second readingoperation is performed.

In a second field, the charge Q1 obtained in the first reading operationand the charge Q2 obtained in the second reading operation aretransferred to the horizontal charge transfer sections 4 a and 4 b,respectively. Then, the charges Q1 and Q2 are transferred through theoutput amplifiers 5 a and 5 b and output terminals 6 a and 6 b assignals S1 and S2.

FIG. 2 also shows the relationship between the timing at which thepulses are input and the level of the charges accumulated in thephotoelectric converting sections 1. The horizontal axis represents thetiming at which the pulses are input, and the vertical axis representsthe quantity of the charge. The solid lines indicate such relationshipwhen the intensity of light is A, the dashed lines indicate suchrelationship when the intensity of light is B, and the chain linesindicate such relationship when the intensity of light is C. Theintensities A, B and C are as shown in FIG. 18.

FIG. 3 is a diagram of a signal processing circuit used in thesolid-state imaging device 100. The signal processing circuit includesinput terminals 7 a and 7 b, a clip circuit 8, and an addition circuit9. The signal processing circuit operates in the following manner.

The signal S1 is input from the output terminal 6 a (FIG. 1) to theinput terminal 7 a and is sent to the clip circuit 8. The clip circuit 8clips a signal having a voltage exceeding a reference voltage Vth,thereby reducing the level of such a signal to the reference voltageVth. The reference voltage Vth is set to be slightly lower thansaturation levels Vsat which correspond to saturation levels Qsat of thephotoelectric converting sections 1. By such an effect of the clipcircuit 8, the influence of non-uniformity among the saturation levelsQsat of the photoelectric converting sections 1 on the operation of thesolid-state imaging device 100 is substantially eliminated.

The signal S2 is sent from the output terminal 6 b to the additioncircuit 9 through an input terminal 7 b. The signal S1 output from theclip circuit 8 and the signal S2 are mixed by the addition circuit 9,and the resulting signal is output from the output terminal 60 as asignal S3.

FIG. 4 is a graph illustrating the photoelectric convertingcharacteristic for the signals S1, S2 and S3. The horizontal axisrepresents the intensity of light, and the vertical axis represents thevoltage of the signals. The solid line indicates such a characteristicof the signal S1, the dashed line indicates such a characteristic of thesignal S2, and the chain line indicates such a characteristic of thesignal S3.

As is shown in FIG. 4, the voltage of the signal S1 reaches thesaturation level of the photoelectric converting section 1 when theintensity of light becomes B. The voltage of the signal S2 reaches thesaturation level of the photoelectric converting section 1 when theintensity of light becomes D. The signal S2 provides a wide dynamicrange, but provides a low S/N ratio when the intensity of light isrelatively low due to the low signal level thereof. The signal S1provides a narrow dynamic range but provides a high S/N ratio due to thehigh signal level thereof. The signal S3 obtained as a result of mixtureof the signals S1 and S2 provides a high S/N ratio even when theintensity of light is relatively low, and also provides a wide dynamicrange.

Where the charge Q1 read by the first reading operation is accumulatedfor time duration t1 and the charge Q2 read by the second readingoperation is accumulated for time duration t2, the dynamic rangeobtained by the signal S3 with respect to the dynamic range obtained bythe signal S1 is t2/t1.

In the solid-state imaging device 100 in the first example, the chargesread by the plurality of reading operations are transferred separately,and the levels of the signals exceeding the reference voltage Vth arelowered to the reference voltage Vth, which is set to be slightly lowerthan the saturation level. In this manner, the influence of thenon-uniformity in the saturation levels of the plurality ofphotoelectric converting sections 1 is substantially eliminated. As aresult, a satisfactory image is displayed.

In the above-described example, two reading operation are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 2

In a second example according to the present invention, the solid-stateimaging device 100 shown in FIG. 1 operates as is illustrated in FIG. 5.øV1 through øV6 are respectively pulses which are input to the drivingpulse input terminals 3 a through 3 f.

In a first field, when light is incident on the solid-state imagingdevice 100, the light is converted into an electric charge by thephotoelectric converting sections 1, and the charge is accumulatedtherein. As is shown in the enlarged section in FIG. 5, in a verticalblanking period of a TV scanning system, a “high” voltage is applied tothe driving pulse input terminals 3 b and 3 e. By such voltageapplication, charges Q1 accumulated in the photoelectric convertingsections 1 a and 1 b are read to the semiconductor regions below thetransfer gates 2 b and 2 e. In this manner, a first reading operation isperformed. The charges Q1 from the photoelectric converting sections 1 aand 1 b which are adjacent to each other in the direction of the column(corresponding to two adjacent pixels) are mixed together.

Within the same vertical blanking period, a “high” voltage is applied tothe driving pulse input terminals 3 b and 3 e. By such voltageapplication, charges Q2 accumulated in the photoelectric convertingsections 1 a and 1 b are read to the semiconductor regions below thetransfer gates 2 b and 2 e independently from the charges Q1. In thismanner, a second reading operation is performed. The charges Q2 from thephotoelectric converting sections 1 a and 1 b which are adjacent to eachother in the direction of the column are mixed together.

In a second field, the charges Q1 obtained in the first readingoperation and the charges Q2 obtained in the second reading operationare transferred to the horizontal charge transfer sections 4 a and 4 b,respectively. Then, the charges Q1 and Q2 are transferred through theoutput amplifiers 5 a and 5 b and output terminals 6 a and 6 b assignals S1 and S2.

FIG. 5 shows the relationship between the timing at which the pulses areinput and the quantity of the charges accumulated in the photoelectricconverting sections 1. The horizontal axis represents the timing atwhich the pulses are input, and the vertical axis represents thequantity of the charge. The solid lines indicate such relationship whenthe intensity of light is A, the dashed lines indicate such relationshipwhen the intensity of light is B, and the chain lines indicate suchrelationship when the intensity of light is C.

The signals S1 and S2 are processed in the same manner by a signalprocessing circuit having the same structure as in the first example.

The resultant signal S3 provides a wide dynamic range and also providesa high S/N ratio even when the intensity of light is relatively low.

In the second example, the charges from two adjacent photoelectricconverting sections are mixed together in the vertical charge transfersection 2. Accordingly, the quantity of the resultant charge is twice ashigh as the quantity of the charge which is obtained without the mixturefor the same intensity of light. As a result, the sensitivity of thesolid-state imaging device 100 is improved.

In the above-described example, two reading operations are performedduring the vertical blanking period. In order to perform the firstreading operation during an effective scanning period before thevertical blanking period, the solid-state imaging device needs to be ofa frame inter-line transfer type provided with a charge accumulatingsection or needs to be provided with an external memory. Performing aplurality of reading operations during the vertical blanking periodallows the use of an inter-line transfer solid-state imaging devicehaving a simpler structure with no frame memory.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 3

A solid-state imaging device 300 in a third example according to thepresent invention will be described with reference to FIGS. 6 and 7.

FIG. 6 is a schematic partial plan view illustrating a structure of asolid-state imaging device 300 in the third example. The solid-stateimaging device 300 includes a plurality of photoelectric convertingsections 1 arranged in a matrix, namely in rows and columns. Eachphotoelectric converting section 1 acts as a light receiving element andcorresponds to one pixel. The solid-state imaging device 300 furtherincludes a plurality of vertical charge transfer sections 2, drivingpulse input terminals 3 a through 3 p, horizontal charge transfersections 4 a, 4 b and 4 c, output amplifiers 5 a, 5 b and 5 c, andoutput terminals 6 a, 6 b and 6 c. Each of the plurality of verticalcharge transfer sections 2 includes a plurality of transfer gates and aplurality of semiconductor regions below (not shown) the respectivetransfer gates. The transfer gates in each vertical charge transfersection 2 are arranged in a line. The plurality of vertical chargetransfer sections 2 and the plurality of columns of photoelectricconverting sections 1 are provided to be adjacent to each other. Foursuccessive photoelectric converting sections 1 a, 1 b, 1 c and 1 d inthe same column form a set. The photoelectric converting section 1 a isadjacent to four transfer gates 2 a, 2 b, 2 c and 2 d; and thephotoelectric converting section 1 b is adjacent to four transfer gates2 e, 2 f, 2 g and 2 h. The other photoelectric converting sections areeach adjacent to four transfer gates in the same manner. The transfergates 2 a through 2 p are connected to the driving pulse input terminals3 a through 3 p, respectively. Although not shown in FIG. 6 completely,all the transfer gates are respectively connected to the driving pulseinput terminals. The horizontal charge transfer sections 4 a through 4c, the output amplifiers 5 a through 5 c, and the output terminals 6 athrough 6 c are provided in a similar manner as in the first example.

FIG. 7 is a timing chart illustrating the operation of the solid-stateimaging device 300. φV1 through φV16 are respectively pulses which areinput to the driving pulse input terminals 3 a through 3 p. In FIG. 7,the chain lines indicate that the pulses are input repeatedly in thesame manner.

The solid-state imaging device 300 operates in the following manner.

In a first field, when light is incident on the solid-state imagingdevice 300, the light is converted into an electric charge by thephotoelectric converting sections 1, and the charge is accumulatedtherein. In a vertical blanking period of a TV scanning system, a “high”voltage is applied to the driving pulse input terminals 3 a, 3 e, 3 iand 3 m. By such voltage application, charges Q1 accumulated in thephotoelectric converting sections 1 a through 1 d are read to thesemiconductor regions below the transfer gates 2 a, 2 e, 2 i and 2 m. Inthis manner, a first reading operation is performed. The vertical chargetransfer sections 2 accumulate the charges independently. In thismanner, a first reading operation is performed.

Within the same vertical blanking period, a “high” voltage is applied tothe driving pulse input terminals 3 a and 3 e. By such voltageapplication, charges Q2 accumulated in the photoelectric convertingsections 1 a and 1 b are read to the semiconductor regions below thetransfer gates 2 a and 2 e independently from the charges Q1. Thecharges Q2 from the photoelectric converting sections 1 a and 1 b aremixed together. In this manner, a second reading operation is performed.Immediately after the second reading operation is finished, the chargesremaining in the photoelectric converting sections 1 are discharged tothe substrate of the solid-state imaging device 300.

In a second field, the charges Q1 obtained in the first readingoperation are transferred to the horizontal charge transfer sections 4 aand 4 b, and the charges Q2 obtained in the second reading operation aretransferred to the horizontal charge transfer section 4 c. Then, thecharges Q1 are transferred through the output amplifiers 5 a and 5 b andoutput terminals 6 a and 6 b as signals S1, and the charges Q2 aretransferred through the output amplifier 5 c and output terminal 6 c asa signal S2.

The signal S1 read by the first reading operation provides a highresolution in the vertical direction because the charges are not mixedto obtain the signal S1. The signal S2 can provide satisfactory tonecharacteristics of a high luminance area of the image, even though thesignal S2 read by the second reading operation provides a low verticalresolution because the signal S2 is obtained as a result of the mixtureof the charges.

In the third example, the charges read by at least one of the pluralityof reading operations are mixed together in the vertical charge transfersection 2, and the charges read by the other reading operations aretransferred with no mixture. In this manner, a wide dynamic range and ahigh vertical resolution are both realized.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 4

A solid-state imaging device 400 in a fourth example according to thepresent invention will be described with reference to FIGS. 8 through10.

FIG. 8 is a schematic plan view of the solid-state imaging device 400.The solid-state imaging device 400 has the same structure as that of thesolid-state imaging device 100 in the first example except that eachphotoelectric converting section 1 is provided with one of four types ofcolor filters. The four types of color filters have differentspectroscopic characteristics to provide colors of magenta (Mg), green(G), yellow (Ye) and cyan (Cy), respectively. The color filters arearranged in the same manner as by a conventional color difference linesequential method reported in the Technical Report of the Institute ofTelevision Engineers, TEBS 87-6, Ed. 694.

The solid-state imaging device 400 operates in the same manner asdescribed in the second example except that the charges to be mixed inthe first field and the second field need to be read from differentcombinations of photoelectric converting sections for interlace.

FIG. 9 is a diagram of a signal processing circuit used for thesolid-state imaging device 400. The signal processing circuit includesinput terminals 7 a and 7 b, color separation circuits 10 a and 10 b,amplifiers 11 a, 11 b, and 11 c, comparators 12 a, 12 b and 12 c,multiplexers 13 a, 13 b and 13 c, and output terminals 60 a, 60 b and 60c. The amplifiers 11 a, 11 b, and 11 c , the comparators 12 a, 12 b and12 c, and the multiplexers 13 a, 13 b and 13 c are included in asynthesis circuit 71.

The color separation circuits 10 a and 10 b each receive a signalobtained as a result of mixture of the charges (Mg+Ye, Mg+Cy, G+Ye, orG+Cy) and outputs RGB colors corresponding to the signal received.

The signal processing circuit operates in the following manner.

The signal S1 read by the first reading operation is sent from theoutput terminal 6 a to the input terminal 7 a and divided into threesignals R1, G1 and B1 by the color separation circuit 10 a. The signalS2 read by the second reading operation is sent from the output terminal6 b to the input terminal 7 b and divided into three signals R2, G2 andB2 by the color separation circuit 10 b. The signals R2, G2 and B2 areamplified by the amplifiers 11 a, 11 b and 11 c, respectively. Theresultant signals are sent to the multiplexers 13 a, 13 b and 13 c,respectively. The signals R1, G1 and B1 are also sent to themultiplexers 13 a through 13 c, respectively. Where the charges Q1 areaccumulated in the photoelectric converting sections for time durationt1 and the charges Q2 are accumulated in the photoelectric convertingsections for time duration t2, the amplification factor of each of theamplifiers 11 a through 11 c is t1/t2. The signals R1, G1 and B1 arealso sent to the comparators 12 a, 12 b and 12 c and compared withreference signal levels R0, G0 and B0, respectively. Thus, thecomparators 12 a, 12 b and 12 c output control signals to themultiplexers 13 a through 13 c, respectively. In the case when thelevels of the signals R1, G1 and G1 are equal to or higher than thereference signal levels R0, G0 and B0, the amplified signals R2, G2 andB2 are selected and output to the output terminals 60 a, 60 b and 60 cas signals R3, G3 and B3 by the multiplexers 13 a, 13 b, and 13 c,respectively. In the case when the levels of the signals R1, G1 and B1are lower than the reference signal levels R0, G0 and B0, the signalsR1, G1 and B1 are selected and output to the output terminals 60 a, 60 band 60 c as signals R3, G3 and B3.

FIG. 10 is a graph illustrating the photoelectric convertingcharacteristics of the signals. The horizontal axis represents theintensity of light, and the vertical axis represents the voltage of thesignals. The solid line indicates such a characteristics of the signalR1, G1 and B1, the dashed line indicates such a characteristic of thesignal R2, G2 and B2, and the chain line indicates such characteristicsof the signal R3, G3 and B3. As is appreciated from FIG. 10, the signalsR3, G3 and B3 provide a wider dynamic range than the signals R1, G1 andB1.

In the fourth example, the photoelectric converting sections areprovided with color filters having different spectroscopiccharacteristics from one another. A plurality of reading operations areperformed during a time duration in which images for one image plane areformed, and the charges read by the reading operations are transferredto the vertical charge transfer section separately. The signals based onthe respective charges are divided into three signals for the RGB colorsand synthesized by the synthesis circuit. As a result, a color imagehaving a wide dynamic range can be displayed by the single solid-stateimaging device 400.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 5

In a fifth example according to the present invention, the solid-stateimaging device 400 is provided with a signal processing circuit shown inFIG. 11.

FIG. 11 is a block diagram of the signal processing circuit in the fifthexample. The signal processing circuit includes input terminals 7 a and7 b, a clip circuit 8, an addition circuit 9, a color separation circuit10, a deknee circuit 14, and output terminals 60 a, 60 b and 60 c. Theclip circuit 8, the addition circuit 9, and the deknee circuit 14 areincluded in a synthesis circuit 72.

The signal S1 read by the first reading operation is sent to inputterminal 7 a and further to the clip circuit 8. A signal having avoltage equal to or higher than a reference voltage Vth is clipped bythe clip circuit 8, thereby reducing the level of such a signal to thereference voltage Vth. The reference voltage Vth is set to be a carriersaturation level Vsat at which color separation is possible. The signalS2 read by the second reading operation is sent to the input terminal 7b and further to the addition circuit 9. The signal from the clipcircuit 8 is also sent to the addition circuit 9 and mixed with thesignal S2. The resultant signal is sent to the deknee circuit 14 as asignal S3. The deknee circuit 14 provides the signal S3 with linearphotoelectronics converting characteristics as is shown in FIG. 12, andthe resulting signal is output to the color separation circuit 10 as asignal S4.

The deknee circuit 14 is one example of a tone compensation circuit forcompensating for a tone characteristics of a signal and has, forexample, a similar structure as that of a gamma compensation circuitused in a video camera. For digital signal processing, a ROM table, forexample, is used.

The signal S4 is divided into signals R, G and B by the color separationcircuit 10, and the signals R, G and B are output from the outputterminals 60 a through 60 c.

In the fifth example, the signals based on the charges separately readby the plurality of reading operations performed by the solid-stateimaging device provided with color filters having differentspectroscopic characteristics are mixed, and the color separation of theresultant signal is then performed. Accordingly, the signal processingcircuit requires only a single color separation circuit.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 6

In a sixth example according to the present invention, the solid-stateimaging device 400 is provided with a signal processing circuit shown inFIG. 13.

FIG. 13 is a block diagram of the signal processing circuit in the sixthexample. The signal processing circuit includes input terminals 7 a and7 b, a color separation circuit 10, an amplifier 11, a comparator 12, amultiplexer 13, and output terminals 60 a through 60 c. The amplifier11, the comparator 12, and the multiplexer 13 are included in asynthesis circuit 73.

The signal S2 obtained by the second reading operation of thesolid-state imaging device 400 is sent to input terminal 7 b, isamplified by the amplifier 11, and is sent to the multiplexer 13. Thesignal S1 obtained by the first reading operation of the solid-stateimaging device 400 is sent to the input terminal 7 a and further to themultiplexer 13. Where the charges Q1 are accumulated in thephotoelectric converting sections for time duration t1 and the chargesQ2 are accumulated in the photoelectric converting sections for timeduration t2, the amplification factor of the amplifier 11 is t1/t2. Thesignal S1 is also sent to the comparator 12 and compared with areference signal level S0. Thus, a control signal is output from thecomparator 12 to the multiplexer 13. In the case when the level of thesignal S1 is equal to or higher than the reference level S0, theamplified signal S2 is selected. In the case when the level of thesignal S1 is lower than the reference level S0, the signal S1 isselected. The selected signal is input to the color separation circuit10 as a signal S3, and divided into signals R, G, B. The signals R, G, Bare output to the output terminals 60 a through 60 c.

In the sixth example, one of the signals based on the charges separatelyread by the plurality of reading operations performed by the solid-stateimaging device provided with color filters having differentspectroscopic characteristics are amplified at a prescribedamplification factor and mixed with the other signals which is notamplified. Then, color separation of the resultant signal is performed.Accordingly, the signal processing circuit requires only a single colorseparation circuit.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 7

In a seventh example according to the present invention, the solid-stateimaging device 400 is provided with a signal processing circuit shown inFIG. 14.

FIG. 14 is a block diagram of the signal processing circuit in theseventh example. The signal processing circuit includes input terminals7 a and 7 b, a color separation circuit 10, an amplifier 11, acomparator 12, a multiplexer 13, a subtraction circuit 15, and outputterminals 60 a through 60 c. The amplifier 11, the comparator 12, themultiplexer 13, and the subtraction circuit 15 are included in asynthesis circuit 74.

The signal S2 obtained by the second reading operation of thesolid-state imaging device 400 is sent to input terminal 7 b and furthersent to the subtraction circuit 15. The signal S1 obtained by the firstreading operation of the solid-state imaging device 400 is sent to theinput terminal 7 a. The subtraction circuit 15 subtracts the signal S2from the signal S1 and outputs the resultant signal to the multiplexer13. The signal S2 is also amplified by the amplifier 11 withoutsubtraction and sent to the multiplexer 13. Where the charges Q1 areaccumulated in the photoelectric converting sections for time durationt1 and the charges Q2 are accumulated in the photoelectric convertingsections for time duration t2, the amplification factor of the amplifier11 is (t1−t2)/t2. The signal S1 is also sent to the comparator 12 andcompared with a reference signal level S0. Thus, a control signal isoutput from the comparator 12 to the multiplexer 13. In the case whenthe level of the signal S1 is equal to or higher than the referencelevel S0, the signal from the amplifier 11 is selected. In the case whenthe level of the signal S1 is lower than the reference level S0, thesignal from the subtraction circuit 15 is selected. The selected signalis input to the color separation circuit 10 as a signal S3, and dividedinto signals R, G, B. The signals R, G, B are output to the outputterminals 60 a through 60 c.

FIG. 15 is a graph illustrating the photoelectric convertingcharacteristic of the signals S1, S2 and S3. As is appreciated from FIG.15, the signal S3 has a much wider dynamic range than the signal S1 orS2.

Generally in an inter-line solid-state imaging device, white linesappear in a vertical direction on a picture (referred to as “smear”) bythe influence of light leaking to the vertical charge transfer section.The quantity of the charge causing smear is constant with respect to thepixels arranged in a vertical line regardless of the time durationduring which the charges are accumulated. In the seventh example, thesignals based on the charges separately read by the plurality of readingoperations are treated with subtraction. Therefore, the charge causingsmear is canceled and a signal which does not generate smear isobtained.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

EXAMPLE 8

A solid-state imaging device 800 in an eighth example according to thepresent invention will be described with reference to FIGS. 16 and 17.

FIG. 16 is a schematic plan view of the solid-state imaging device 800.The solid-state imaging device 800 has the same structure as that of thesolid-state imaging device 300 in the third example except that eachphotoelectric converting section 1 is provided with one of four types ofcolor filters. The four types of color filters have differentspectroscopic characteristics to provide colors of magenta (Mg), green(G), yellow (Ye) and cyan (Cy), respectively. The color filters arearranged in the same manner as explained in Example 4.

The solid-state imaging device 800 operates in the same manner asdescribed in the third example except that the charges to be mixed inthe first field and the second field need to be read from differentcombinations of photoelectric converting sections for interlace.

FIG. 17 is a diagram of a signal processing circuit for the solid-stateimaging device 800. The signal processing circuit includes inputterminals 7 a, 7 b and 7 c, color separation circuits 10 a and 10 b,amplifiers 11 a, 11 b, and 11 c, comparators 12 a, 12 b and 12 c,multiplexers 13 a, 13 b and 13 c, and output terminals 60 a, 60 b and 60c. The amplifiers 11 a, 11 b, and 11 c, the comparators 12 a, 12 b and12 c, and the multiplexers 13 a, 13 b and 13 c are included in asynthesis circuit 75.

The color separation circuit 10 b receives a signal obtained as a resultof the mixture of the charges (Mg+Ye), Mg+Cy, G+Ye, or G+Cy) and outputssignals R2, G2 and B2. The color separation circuit 10 a receives asignal obtained without mixture of the charges (Mg, G, Cy and Ye) andoutputs signals R1, G1 and B1.

The signal processing circuit operates in the following manner.

The signal S1 obtained by the first reading operation is sent to theinput terminals 7 a and 7 b and divided into three signals R1, G1 and B1by the color separation circuit 10 a. The signal S2 obtained by thesecond reading operation is sent to the input terminal 7 c and dividedinto three signals R2, G2 and B2 by the color separation circuit 10 b.The signals R1, G1, B1, R2, G2 and B2 are processed in the same manneras in the fourth example.

The signal S1 which is input to the color separation circuit 10 aprovides a high vertical resolution because no mixture of charges isperformed to obtain the signal S1. Accordingly, a signal providing ahigh vertical resolution is obtained.

In the eighth example, the photoelectric converting sections areprovided with color filters having different spectroscopiccharacteristics from one another. The charges read by at least one ofthe plurality of reading operations are mixed in the vertical chargetransfer section 2, and the other charges are transferred with nomixture. As a result, a color image having a wide dynamic range can bedisplayed by the single solid-state imaging device 800.

In the above-described example, two reading operations are performed. Inan alternative method, three or more reading operations are performedusing a different structure for the vertical charge transfer section 2.

As has been described so far, according to the present invention, thecharges read by a plurality of reading operations from a plurality ofphotoelectric converting sections are transferred separately by thesolid-state imaging device as signals. Signals having a level exceedinga saturation level are clipped to reduce the levels of such signalssubstantially to the saturation level. In this manner, the influence ofthe non-uniformity in the saturation levels among the photoelectricconverting sections is substantially eliminated. As a result,satisfactory image quality is obtained.

In the case when the charges from two adjacent photoelectric convertingsections are mixed in the vertical charge transfer section, the level ofthe resultant charge is twice as high as the level of the charge whichis obtained without such mixture with respect to the same intensity oflight. Accordingly, the sensitivity of the solid-state imaging device isimproved.

Since the plurality of reading operations are performed within avertical blanking period, the solid-state imaging device requires noframe memory and thus the structure thereof is simplified.

In the case when the charges from two adjacent photoelectric convertingsections in at least one of the plurality of reading operations aremixed in the vertical charge transfer section and the remaining chargesare transferred without such mixture, a wider dynamic range and a highervertical resolution are obtained.

By providing the photoelectric converting sections with color filtershaving different spectroscopic characteristics from one another, a colorimage can be displayed.

In the case when the signals obtained by the solid-state imaging deviceare divided into RGB color signals by a color separation circuit andthen synthesized, a color image having a wider dynamic range can beobtained by a single solid-state imaging apparatus.

In the case when the signals obtained by the solid-state imaging deviceare synthesized and then divided into RGB color signals, only one colorseparation circuit is required, thus simplifying the structure of thesignal processing circuit.

In the case when a part of the signals obtained by the solid-stateimaging device are treated with subtraction and another part of thesignals are amplified at a constant amplification factor, and the signalobtained as a result of the subtraction or the signal obtained as aresult of the amplification is selected, smear is substantiallyeliminated from the resultant image.

In the case when the charges from two adjacent photoelectric convertingsections in at least one of the plurality of reading operations aremixed in the vertical charge transfer section and the remaining chargesare transferred without such mixture, in the state where thephotoelectric converting sections are provided with color filters havingdifferent spectroscopic characteristics, a color image having a widerdynamic range and a higher vertical resolution can be obtained by asingle solid-state imaging apparatus.

Various other modifications will be apparent to and can be readily madeby those skilled in the art without departing from the scope and spiritof this invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the description as set forthherein, but rather that the claims be broadly construed.

What is claimed is:
 1. A solid-state imaging apparatus, comprising: asolid-state imaging device including: a plurality of photoelectricconverting sections provided with color filters having differentspectroscopic characteristics and; charge transfer means, including aplurality of vertical charge transfer sections, for transferring aplurality of charges read from each of the photoelectric convertingsections to a plurality of receiving elements, wherein a first readingoperation is performed for providing a first charge accumulated in atleast one photoelectric converting section to the charge transfer means,a second reading operation is performed for providing a second chargeaccumulated in the at least one photoelectric converting section to thecharge transfer means, the first and second charges remain separatewithin the charge transfer means, the first and second charges each heldin a respective one of said vertical charge transfer sectionssimultaneously, and wherein the first charge provided by the firstreading operation and the second charge provided by the second readingoperation are transferred from the charge transfer means to thereceiving elements substantially simultaneously without transferring thefirst and second charges between the first reading operation and thesecond reading operation, the first charge is transferred separatelyfrom the second charge to the receiving elements and a signal processingcircuit including: a synthesis circuit for synthesizing signals based onthe first charge provided by the first reading operation and the secondcharge provided by the second reading operation, and a color separationcircuit for performing color separation of the signals sent by thesynthesis circuit and outputting the resultant signals.
 2. A solid-stateimaging apparatus according to claim 1, wherein the synthesis circuitincludes: a clip circuit for receiving a first part of the signals basedon the first charge provided by the first reading operation and thesecond charge provided by the second reading operation and clipping thesignals each having a level exceeding a prescribed level to reduce thelevels of such signals to the prescribed level; an addition circuit foradding the signals sent by the clip circuit and a second part of thesignals; and a tone compensation circuit for compensating for tonecharacteristics of the signals sent by the addition circuit.
 3. Asolid-state imaging apparatus according to claim 1, wherein thesynthesis circuit includes: an amplification circuit for receiving afirst part of the signals based on the first charge provided by thefirst reading operation and the second charge provided by the secondreading operation and amplifying the first part of the signals at aconstant amplification factor; a comparison circuit for comparing asecond part of the signals with a reference signal level; and aselection circuit for selecting one of the first part and the secondpart, based on the output from the comparison circuit.
 4. A solid-stateimaging apparatus according to claim 1, wherein the synthesis circuitincludes: a subtraction circuit for subtracting a second part of thesignals based on the first charge provided by the first readingoperation and the second charge provided by the second reading operationfrom a first part of the signals; an amplification circuit foramplifying the second part of the signals at a constant amplificationfactor; a comparison circuit for comparing the first part of the signalswith a reference signal level; and a selection circuit for selecting oneof the signals sent by the amplification circuit and the signals sent bythe subtraction circuit, based on the output from the comparisoncircuit.